I see an number of posts stating the R7.0 is to be used to create the high point for datum C this is incorrect as the R7 cannot produce the high point..
Datum C is the tangent of the radius 19.8 that is struck from the centre diameter.
I would measure the radius 19.8 then intersect it with a generic line to create the point C Datum
Except that you won't be able to get a reliable radius measurement on such a small portion of surface. The method I described earlier is the closest way of simulating how an actual gauge would contact. You need to align to your datum A and B features, add in the theoretical 12.5° rotation back to centre line and then sample the surface where datum C is supposed to contact. You can gather points on that surface any way you see fit - vector points, scans etc. The density of those points will dictate how likely you are to pick up the true contact point of datum C.
Except that you won't be able to get a reliable radius measurement on such a small portion of surface. The method I described earlier is the closest way of simulating how an actual gauge would contact. You need to align to your datum A and B features, add in the theoretical 12.5° rotation back to centre line and then sample the surface where datum C is supposed to contact. You can gather points on that surface any way you see fit - vector points, scans etc. The density of those points will dictate how likely you are to pick up the true contact point of datum C.
